Hydrocarbon fuels generally contain numerous deposit-forming substances. When used in internal combustion engines (ICEs), deposits tend to form on and around constricted areas of the engine which are in contact with the fuel. In automobile engines deposits can build up on engine intake valves leading to progressive restriction of the gaseous fuel mixture flow into the combustion chamber and to valve sticking. There are two general types of inlet valve deposits, heavy deposits and thin deposits. These different types of deposits affect the performance of the fuel and the engine in slightly different ways. Heavy deposits are carbonaceous and oily in appearance. They cause flow restriction past the valves, which in turn reduces the maximum power of the engine, decreasing fuel economy and increasing emissions. Thin deposits tend to cause problems on starting the engine and increasing emissions.
As engines become more sensitive to deposits, it has become common practice to incorporate a detergent in the fuel composition for the purposes of inhibiting the formation, and facilitating the removal, of engine deposits, thereby improving engine performance and emissions.
It is known to use certain polyisobutylsuccinimide-derived quaternized PIB/amine dispersants/detergents as additives in fuel compositions. Polyisobutylsuccinimides may also be described as polyisobutylene succinimides. These quaternized dispersants/detergents are derived from traditional PIB/amine fuel additive compounds that have pendant tertiary amine sites which can be alkylated, i.e. quaternized, by a quaternizing agent, such as propylene oxide. Examples of these additives are disclosed in U.S. patent application US 2008/0307698.
However, there is a need for additives that provide the benefits described above while also exhibiting improved thermal stability and/or oil compatibility properties. There is also a need for additives that provide the benefits described above more efficiently, thus allowing for the use of lower additive treat rates while obtaining the same performance, thus reducing the cost and environmental impact of the additives as well as the compositions in which they are used. There is also a need for additives that provide the benefits described above which are less energy intensive to produce.
The present invention deals with a new class of detergents which offer significant improvements over traditional PIB/amine detergents, including polyisobutylsuccinimide-derived quaternized detergents. A new class of quaternized PIB/amines derived from polyisobutenyl succinamides and/or esters have now been discovered. These additives are more thermally stable than the imide variant and may be manufactured by a less energy-intensive process. The quaternized additives of the present invention not only perform at least equally as well as comparable polyisobutenyl succinimide quaternized additives, but can also provide that performance more efficiently and/or with improved thermal stability and/or oil compatibility.